Relationship between a Female Guppy’s Anal Fin and a Male’s Mating Behaviors

Abstract

Sexual selection and the various factors that apply to it are important topics that researchers have studied
for years. Sexual selection, a theory by Darwin, is a form of natural selection in which a male or female
is attracted to certain physical characteristics or behaviors when mating, causing a genetic change in the
species. In our experiment, we measured the mate choice of male guppies (Poecilia reticulata) on female
guppies with and without anal fins. To do this, we used two orange 3D guppy models, one without an
anal fin and one with an anal fin, and placed them in either side of the tank while measuring how many
mating behaviors were displayed to each model and how much time was spent on each side of the tank.
Each trial lasted five minutes. We hypothesized that the male guppy would be more attracted to the
female with the anal fin because the fin is used in reproduction. The results support our hypothesis
because, on average, the male guppy spent more time on the side of the tank with the female model with
the anal fin and displayed more mating behaviors toward this model as well. In comparison to other
studies about how anal fins affect mate selection, our experiment had completely opposite results. Our
study adds research to how the fins of female guppies influence male mate choice, which is beneficial
because the majority of sexual selection experiments involve the ornamentation of size of female models.